Insulated bayonet tube vaporizer



Jan. 12, 1954 P. s. OTTEN INSULATED BAYONET TUBE VAPORIZER Filed Feb. 3,1951 FIG. I

' INVENTVOR 42? 6: Offer? Pfiz/ ATTORNEYS Patented Jan. 12, 1954 PhilipS. Otte'n; New Rochelle, N. Y.,.assig-nor to" The Griscom RussellCompany,. New York, N. Y., a-corporation of Delaware:

ApplicationFebruar'y 3, 1951, SerialNo'. 209,227

1 Claim.

This invention" relates toliquefied g'as vaporizers of the type usedprimarily for restoring to gaseous. form at atmospheric temperatures andpressures gases which have been liquefied for storage, transportation orother purposes. The boiling point of liquefied gases such as natural gasat atmospheric pressure is very 1ow,.in the order of 250 F. Natural gascan be liquefied and stored in insulated tanks and then revaporized andreturned to the gas mains to supply peak load demands, thereby making itpossible to supply the needs of a municipality or an industrial user ofgas Without providing pipeline facilities of a capacity necessary tomaintain peak load operations. For industrial establishments a peak loadcapacity of short duration several times the normal load is frequentlyrequired, and such condition may be economically met by liquefying gasduring low load intervals for utilization to meet peak load demands.

For vaporizing liquefied gas of this character it has been the practiceheretofore to use a shell and tube apparatus such as disclosed in U. S.Patent No. 2,273,257, wherein the liquefied gas to be vaporized isheated by steam in the shell of the apparatus, the liquefied gas beingdelivered to the inner tubes of double-tube elements so that the steamconstituting the heating medium does not directly contact the walls ofthe tubes through which the cold liquid enters the apparatus.

With the apparatus described in the above mentioned patent the liquefiednatural gas can be vaporized with exhaust steam as the heating medium ina satisfactory and economical manner, and such apparatus has been incontinuous commercial use for years. However, in some cases it has beenfound that the vaporized gas leaving the apparatus varies considerablyin temperature so that when the gas is delivered to the mains and addedto the normal gas supply, difiiculty has been experienced in maintainingthe desired constant pressure in the gas mains. In some instances it hasbeen found desirable to interpose a heat exchanger between thevaporizing unit and the gas main to maintain the vaporized gas at auniform temperature, so that its addition to the gas mains will notresult in undesirable pressure variations.

I have found that this variation in delivery temperature of the.vaporized gas from vaporizing units constructed in accordance with theabove mentioned patent is largely due to variations in the reabsorptionof heat by the vaporized gas at the discharge end of the vaporizer tubesfromthe Iiq'uidgas as it enters the inner tube ofthe vaporizer element,and the invention of the present application constitutes an improvementon the apparatus of the above mentioned patent whereby a more uniformdischarge temperature of the vaporized gas may be maintained.

In the accompanying drawings I have illustrated a preferred embodimentof my improvement, and in the said drawings,

Fig. 1 is a side elevation partly broken away of a liquid gas vaporizerembodying my improvements; and

Fig. 2 is a vertical sectional view on an enlarged scale of one of thevaporizing elements.

Referring to the drawings, particularly Fig. 1, l indicates the shell ofthe apparatus to which the exhaust steam is delivered through an opening2 at the top, the condensate being withdrawn through a discharge openingit near the bottom of the shell. The shell is fianged at its open bottomend and is seated on a tube sheet 3 forming the upper Wall of a gas discharge header 4. Seated in the tube sheet 3 are the outer tubes 5 of thevaporizer elements, the structure of which is shown in detail in Fig. 2.Each vaporizer element comprises an outer tube 5 closed at its upper endand an inner tube 6 seated in a lower tube sheet I forming the bottomwall of the discharge chamber 4 and projecting upwardly within the tube5 to a point near the top of said tube. Underlying the tube sheet 1 isan end cap 8 forming an inlet chamber for the liquefied gas which isdelivered to the apparatus through the inlet openin 9.

In the apparatus disclosed in the above mentioned patent the inner tubes6 of the vaporizer element are provided with longitudinal fins toincrease the heat transfer surface of the tubes 6 and thereby increasethe heat transfer from the liquefied gas in the tube 8 to the vaporizedgas in the annular space between the inner and outer tubes. I havefound, however, that this increase in the heat transfer from theliquefied gas to the vaporized gas does not have the effect ofincreasing the overall efiiciency of the apparatus, but on the contraryresults in lowering the discharge temperature of the vaporized gas andalso makes it difiicult to maintain a uniform discharge temperature ofthe vaporized gas. I have found that this difiiculty can be largelycorrected by constructing the inner tube 6 of two concentric sectionsseparated from each other in a manner to reduce heat conduction so thatthe outer wall of the double tube section Will.

throughout its length be at a substantially higher temperature than theinner wall section which is in direct contact with the liquefied gas,thereby reducing instead of increasing, the heat transfer from theliquefied gas in the inner tube to the vaporized gas in the spacebetween the inner tube 8 and outer tube 5.

In the construction illustrated in the drawing, the inner tube 6 of thevaporizing element is surrounded by a concentric tube section I lseparated from the tube 6 by a spacing wire 12 which is wound around thetube 6 and spot-welded thereto at intervals. The tube H rests at itslower end against the face of the tube sheet 3 closing the end of theannular space between the tubes 6 and I l and thereby forming betweenthe tubes a dead air space which serves to reduce the rate of heattransfer between the liquefied gas in the tube 5 and the vaporized gasin contact with the exposed surface of the tube l I. By

so constructing the inner tubes of the heat ex-.

change element the transfer of heat from the exposed surface of the tubeH to the vaporized gas in the discharge chamber 4 is negligible, therebymaking it easier to maintain the vaporized gas at a uniform dischargetemperature of the desired value.

In the foregoing specification and accompanying drawings I have shownand described my im- 4 provement in the preferred form in which it hasbeen developed for commercial installation, but it is to be understoodthat the invention is not limited to the construction shown anddescribed except insofar as included in the accompanying claim.

I claim:

In a liquefied gas vaporizer, a heat exchange element consisting of anouter tube closed at the end, an inner tube projecting into said outertube through its open end, said inner tube consisting of inner and outertube sections and a separator between said tube sections comprising awire of a diameter equal to the space between said tube sections, saidwire being wound helically around the inner tube section, and a closurefor the space between the tube section at one end.

- PHILIP S. OTTEN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,361,075 Wiese Oct. 24, 1944- FOREIGN PATENTS Number CountryDate 122,563 Great Britain Jan. 30, 1919

